When I began doing research on the Oxalis bulb, I knew it as the yellow "sour grass" that is pretty, but a pest that grows in my lawn and garden, and as a potted plant that can be found in stores, usually during the winter, to brighten up your windowsill. I had no idea whether they were related or not, though they shared the same name and had the same clover-type leaves, even though the house plants that I have seen had red leaves. Now, after much study, I have discovered that there are about 800 different species of this small bulb, worldwide, some of which are native to the US. They can be hardy or tender, low-growing, tall, colonizing or invasive. Some are also shrubby, growing to 8'. The plants can be used in the garden or potted in the house and many share the trait of closing up in the evening or on cloudy days.

The plant that just about everyone is familiar with is Common Yellow Oxalis (Oxalis stricta), also known as Sour Grass or Sorrel. It is an African native and can be found throughout the eastern US into Canada and most of the western states. It is usually growing in our lawns, fields and gardens. As a child, I would pick the leaves and chew on them - they have a slightly sour taste and it is this taste that gives it its name: "Oxalis" meaning "sharp" in Greek and "Sorrel" meaning "acidic" or "sour." The leaves can be used in salads, though ingesting too much can cause problems because the "sourness" is due to oxalic acid, which is toxic in very large doses.

Redwood Sorrel (Oxalis oregana) covers the floors of the Redwood forests in California. It bears white flowers tinged in violet in its wild form, but can be found in pink from nurseries.

Violet Wood Sorrel (Oxalis violacea) is native to the eastern two-thirds of Kansas and is also known as violet oxalis or sheep sorrel. The leaves on this species are gray-green and sometimes have a reddish spot near their base. The flowers are pale purple to pinkish-purple.

White Wood Sorrel (Oxalis acetosella) comes from Eurasia and is sometimes known as "shamrocks." It has a pretty little white flower that can be pink or purple-veined.

Oxalis 'Triangularis,' also known as purple shamrock or lucky shamrock, has purple leaves with deep rose patterning. Flowers are white to light pink. This plant is excellent and eye-catching on the windowsill during the winter.

Oxalis 'Regnelli' is the popular species that is sold as potted shamrocks in March. The plant has bright green leaves and white flowers.

Oxalis Braziliensis, as indicated by its name, is native to Brazil. It is a wonderful house plant and a carefree garden plant in zones 8-10. Leaves are a darker green which show-off the bright pink flowers.

Most of the Oxalidacaea family are easy to grow, petite and inexpensive, making them perfect for containers or groundcovers. The plant tends to bloom outside in the spring but some bloom in mid-winter, just when a touch of color is needed on the windowsill or in the greenhouse.

If you have not included some of these bulbs in your outdoor or indoor garden, you should definitely check out the catalogs and see what suits your planting zone. If your favorite isn't suited to your area, pot it up for your windowsill and bring in some color during the dark days of winter.